The invention relates to a forming machine at least comprising a clamping device for clamping down a hollow workpiece to be deformed, which has at least one open end, a first forming tool which can be placed into contact with the outer surface of the workpiece while the workpiece is being worked, and by means of which the workpiece can be deformed, driving means for rotating said workpiece and said tool about a first axis with respect to each other and means for moving the workpiece and the tool with respect to each other in such a manner that said tool can follow one or more desired paths with respect to the workpiece so as to work said workpiece. The invention furthermore relates to a method by means of which a hollow workpiece having at least one open end can be deformed.
Such an apparatus and method are known, for example from European patent application No. EP 0 916 428. Said publication discloses a forming machine, comprising a forming head fitted with a number of rollers, by means of which the diameter of one end of a cylindrical metal element can be reduced and, in addition, be bent through an angle.
To this end, the metal cylinder is clamped down and the forming head is rotated, whereupon the end is deformed by pressing the rollers in a radial direction against the outer surface of the metal cylinder and moving them along said outer surface in a number of cycles, whereby the radial distance between the rollers and their axis of rotation is decreased with each cycle. Since the axis of rotation is at an angle with the central axis of the non-deformed part of the metal cylinder, the end of the cylinder is not only reduced as a result of the movement in radial direction of the rollers, but in addition the end will also be positioned at an angle. Due to the use of the aforesaid cycles, the workpiece assumes the shape of the final product step by step.
EP 0 916 426 discloses a comparable forming machine and method, wherein the axis of rotation is eccentrically offset from the central axis of the metal cylinder. Thus a product is obtained wherein the central axis of the deformed portion is likewise offset from the central axis of the non-deformed portion of the metal cylinder.
The apparatus and method in hand can e.g. be used in the production of the housings of catalytic converters that form part of the exhaust system of vehicles, such as cars. Such catalytic converters have a diameter which is larger than the diameter of the pipes of the exhaust system of which they form part, and they are preferably positioned close to the engine block in order to reach their operating temperature as quickly as possible after the engine has been started and to maintain that temperature as much as possible. One consequence of this is that, first of all, the diameter of the connections on either side of the catalytic converter housing must be reduced in order to properly connect to the rest of the exhaust system, while in addition they need to have a complicated shape in many cases in order to enable an optimum position with respect to the engine block.
In the above-described apparatuses for producing workpieces having at least one deformed end, such as the above-described catalytic converter housings, the workpiece is held stationary, while the forming head is rotated. Since more and more complex shapes are being required, as already described above, there is a need for versatile and in some cases much larger forming heads. Furthermore, the number of rollers present on and controlled by a single forming head may increase (considerably).
It is an object of the present invention to provide an improved forming machine of the kind referred to in the introduction.